Add missing guild information (#466)

* Add POJO for guild ranks

* Refactor GuildReply & inner classes

* Add "unused" suppression on GuildReply

* Add per-game experience to guild reply

* Make weekly exp accessible for Guild.Member

* Make GetGuildExample more informative

* Add preferredGames support; begin making Guild immutable

* Refactor and document Banner class

* Add a few more comments to example

* Add achievement stats to Guild

* Fix confusing legacyRanking behavior

* Add preferredGames to example

* Add missing quote to javadoc link

Author: TheNullicorn

hypixel-api-core/src/main/java/net/hypixel/api/data/type/GuildAchievement.java

@@ -0,0 +1,32 @@
+package net.hypixel.api.data.type;
+
+/**
+ * Types of achievements that can be earned by guilds on Hypixel.
+ * <p>
+ * Created using <a href="https://github.com/slothpixel/hypixelconstants">slothpixel/hypixelconstants</a>
+ * as a reference.
+ */
+public enum GuildAchievement {
+    /**
+     * A tiered achievement based on the highest amount of experience earned by a guild in a single
+     * day.
+     */
+    EXPERIENCE_KINGS,
+
+    /**
+     * A tiered achievement based on the highest number of members a guild has had online at the
+     * same time.
+     */
+    ONLINE_PLAYERS,
+
+    /**
+     * A tiered achievement based on a guild's highest level.
+     */
+    PRESTIGE,
+
+    /**
+     * A tiered achievement based on the highest number of combined wins (in mini-games) between
+     * members of a guild on the same day.
+     */
+    WINNERS
+}